Cylinder for internal combustion engine



Oct. 16, 1956 J. DOLZA ET AL CYLINDER FOR INTERNAL COMBUSTION ENGINE Filed Sept. 9, 1954 ATTORNEY United States Patent O CYLINDER FOR INTERNAL COMBUSTION ENGINE John Dolza, Davisburg, and Berti] B. Cederleaf, Pontiac,

Mich., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application September 9, 1954, Serial No. 454,995 4 Claims. (Cl. 12341.78)

This invention relates generally to cylinders for internal combustion engines and particularly to cooling systems therefor.

One of the principal objects of this invention is to provide improved cooling means for the exhaust ports and passages of an internal combustion engine cylinder.

Another object of the invention is to provide means for eliminating carbon deposits (coking) in the exhaust ports and passages of an internal combustion engine cylinder.

A further object of the invention is to provide an internal combustion engine cylinder with means for conveying pressurized gaseous coolant to the exhaust ports where it is discharged directly into the exhaust passages and manifolding.

The invention has particular application to the cylinders of two-cycle engines having exhaust ports in the lower part of the cylinder side wall in which relatively high temperatures are developed at widely spaced points; i. e., in the cylinder walls adjacent the ports and in the combustion chamber walls of the cylinder head and the cylinder upper end. In such engines a temperature variation also occurs at the port section due to the differences between the exhaust gas and scavenged air temperatures which results in cylinder distortion in this area. These extremes of temperature variations have created a problem in designing the cooling system for such cylinders, particularly those of the larger sizes, so as to avoid overheating and thermal strains in operation. Further, in the case of engines which are basically designed to operate on either gas or oil (diesel) fuel or a combination thereof, it is desirable that the provision for cooling be adapted for change to meet the changed conditions encountered with either fuel without necessitating the redesign of the basic components of the cylinder unit.

In conventional exhaust port cooling systems for twocycle loopscavenged engines, cooling fluid is caused to pass through longitudinal passages provided in the strut or bridge portions separating adjacent exhaust ports. These passages, especially in water jacketed engines, form part of a closed cylinder cooling system. However, in two-cycle engines employing loop scavenging, the most convenient arrangement for manifolding the inlet and exhaust ports in the cylinder wall is to provide a housing which surrounds circumferential port sections of the cylinder. As the port section and consequently the inlet and exhaust housing are preferably located as close to the engine crankcase as possible for proper cylinder support, there is usually insufiicient space between the manifold housing and the crankcase of the engine for introducing the liquid coolant into that portion of the cylinder side wall for flow between the exhaust ports.

A still further object of the invention is, therefore, to provide improved means for effecting the equalization of circumferential temperature distribution at the port section of a two-cycle loop-scavenged engine cylinder thereby reducing cylinder distortion.

In the main, these objects are accomplished in accordance with the invention as applied, by way of illus- Patented Oct. 16, 1956 tration, to a two-cycle loop-scavenged engine by incorporating means for bleeding a small amount of the cylinder charging air through axial passages formed in the strut portions separating adjacent exhaust ports to effect the cooling of these strut portions and discharging this pressurized air through slits opening into the exhaust passages adjacent the exhaust ports opening on the cylinder proper to cool the port surfaces and with sufiicient velocity to prevent the building up of carbon deposits in the exhaust port opening.

While the invention has particular application to twocycle engine cylinders, its use is not limited to internal combustion engines of this particular type and it is considered adaptable to the exhaust ports and passages of two and four-cycle engines generally.

The aforementioned and other objects of the invention will be more clearly understood from the following description of a representative structure embodying the same in which reference is made to the accompanying drawing, wherein:

Figure l is a longitudinal sectional view through a cylinder unit of an internal combustion engine embodying the principles of the invention.

Figure 2 is a sectional plan view taken substantially on the line 2-2 of Figure 1.

Referring now to the drawing, Figure 1 shows a twocycle loop-scavenged internal combustion engine having a crankcase 12 supporting a cylinder unit indicated generally by the numeral 14. The cylinder unit includes a cylinder casing 16 closed at one end by a head 18 suitably secured thereto or formed integrally therewith. The head 18 is provided with a conventional fuel injector unit as indicated by the numeral 20. The other end of the cylinder casing is suitably attached to the crankcase 12. The internal side wall 30 of the casing 16 is fitted with a cylinder liner 32 which terminates at its upper end against the cylinder head 18. A piston 34 reciprocably mounted within the cylinder liner 32 serves to control air inlet ports 36 and exhaust ports 38 formed circumferentially of the lower portion thereof. The air inlet ports 36 are aligned with and connectable through air inlet passages 40 formed in the cylinder casing 16 to ports 42 opening on a common inlet manifold or air box for supplying pressurized scavenging and charging air which is formed integrally with the crankcase 12. The exhaust ports 38 are similarly aligned with and con nectable through exhaust passages 44 formed in the cylinder casing 16 to a common exhaust manifold, not shown. The number and the size of the inlet and exhaust ports will, of course, depend on the particular operating requirements of the engine, the exhaust ports being circumferentially spaced from each other and disposed in a group on one side of the cylinder, and the inlet ports being similarly grouped and spaced from each other around the remainder of the cylinder circumference.

The adjacent inlet ports and passages in the cylinder liner and cylinder casing are separated by axially extending strut or bridge portions 36a and 36b, respectively, and the adjacent exhaust ports and passages are similarly separated by strut or bridge portions 38a and 38b formed in the cylinder casing 14 and the cylinder liner, respectively. In carrying out the principles of loop scavenging in an etficient manner, the various ports, passages, and the dividing strut portions therebetween should be arranged so as to provide a smooth flow of air into and a smooth expulsion of the combustion gases out of the cylinder. The external surface of each of the cylinder liner exhaust port struts 38b and the internal surface of the adjacent cylinder casing strut 38a are in limited radially spaced relation to each other forming a narrow axial space or slit 46 therebetween which interconnects the adjacent exhaust ports 38 and passages 44.

3 A plurality of axially extending passages 48 are formed in the cylinder casing 16 and bounded by the cylinder 1iner32 and serve to interconnect each of the slits 46 with the crankcase manifold port openings 42.

With the above described cylinder construction embodying one form of the invention, a small amount of the charging .air supply is bled from the crankcase manifold through the axial passages 48 to the slits 46 where it .is discharged into .the exhaust passages 44 adjacent the exhaust ports 38 during the major portion of the cylinder operating cycle. This air flow through the passages 48 and .the slits 46, as well as the expansion of the pressurized air as it passes into the exhaust passages 44, serves to cool the exhaust port struts 38a and 38b. The cooling efiect provided thereby reduces circumferential temperature variation and resultant detrimental distortion occurring at theport section of the: cylinder liner and cylinder casing. The discharge of air through the slits 46 into the passages 44 is generally of sufficient velocity to prevent the formation or build-up of carbon deposits on the surfaces of .the exhaust port openings.

The .fiow of coolant air through the strut cooling passages 48 and the slits 46 will, of course, be dependent on exhaust gas conditions present in the exhaust passages and ,manifolding at a given instant which are in turn related to the exhaust manifold design and its connection with other cylinders of the engine. With properly designed exhaust manifolding for a two-cycle loopscavenged engine, the pressure in the exhaust passages 44 is generally below the pressure of the available scavenging and charging air supply when the exhaust ports 38 are covered by the piston with the exception of brief reactions from the exhaust impulses of the other cylinders connected to the common exhaust manifold. While the pressure impulses occurring in the exhaust passages 44 during initial opening of the exhaust ports is substantially higher than the available charging pressure, the velocity of the exhaust gases flowing into these passages is sufficient so as to aspirate the necessary flow of coolant air from the slit 46. As the piston further approaches bottom dead center, opening the air inlet ports 36, the pressure in the exhaust passages 44 will again drop below the pressure of the charging air in order to provide a proper cylinder scavenging and will remain at slightly below charging pressure until the air inlet ports 36 are substantially closed by the upward stroke of the piston. The upward stroke of the piston compresses the air charge in the cylinder above the air charging pressure and forces a portion. thereof through the exhaust ports 38. During this brief interval of cylinder operation, the air charge escaping through the exhaust ports 38 again tends to aspirate cooling air into the exhaust passage through the slits 46.

While, for the purposes of. illustration, only one specfic embodiment of the invention has been shown and described as utilized in a two-cycle loop-scavenged engine, it is appreciated that various minor modifications may be made without departing from the spirit and scope of the invention as defined in the following claims and that the invention is adapted to internal combustion engines generally having a source of pressurized air associated therewith.

We claim:

1. In a loop-scavenged internal combustion engine, the combination comprising, a cylinder including a casing and a cylinder liner mounted therein, said cylinder casing and said liner having circumferentially disposed exhaust and inlet port sections, each of said port sections having a plurality of ports therein, said ports being separated by aligned strut portions of said casing and said liner, means for supplying pressurized scavenging air to said inlet ports, and longitudinally extending passages formed between adjacent exhaust portstrut portions of said casing and said liner for bleeding a portion of the pressurized air supply therebetween to said exhaust ports.

2. In a two-cycle internal combustion engine, the combination comprising, a cylinder, a piston reciprocably mounted therein, said cylinder having circumferentially disposed exhaust and inlet port sections controllable by said piston, each of said port sections having a plurality of passages opening on said cylinder, said passages being separated by strut portions of said cylinder, means for supplying pressurized scavenging air to said cylinder through said inlet passages, and passages in the strut portions separating said exhaust passages connectable to said pressurized air supplying means for bleeding a portion of the pressurized air supply to said exhaust passages adjacent their openings on said cylinder.

3. A cylinder for an engine including a cylinder casing having a cylinder liner mounted therein, said cylinder casing'and said liner having a plurality of circumferentially spaced aligned exhaust ports, the portions of said cylinder casing between said ports being in limited radially spaced relation to the portion of said liner between said ports 'to form a fluid receiving space therebetween, and means including passages formed in said casing for di recting pressurized air on the external surface of said liner between said ports in said fluid receiving space.

4. A cylinder for an engine having a plurality of circnmferentially spaced exhaust ports opening into said cylinder, partition walls in said cylinder defining and separating said exhaust ports, and means including passages in said partition walls for continuously passing pressurized cooling air into said ports adjacent their openings into said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,113 Griswold Aug. 23, 1932 FOREIGN PATENTS 360,382. Great Britain Dec. 3, 1931 693,959 Germany Dec. 6, 1940 

